1. Field of the Invention
The present invention relates to a buckle apparatus for use in a seatbelt system for a vehicle designed to protect an occupant in an emergency situation of the vehicle.
2. Description of the Related Art
A typical conventional buckle apparatus for use in a seatbelt system for a vehicle has heretofore been arranged such that an occupant can be fastened by an occupant restraining webbing by engaging a tongue plate connected to an end or intermediate portion of the webbing with the buckle apparatus.
There are various types of buckle apparatus. One of them is a latch type buckle apparatus in which, as shown in FIG. 9, a tongue plate 12 is engaged with a lock member 10 which has its two ends respectively supported by buckle body members 14. This latch type buckle apparatus has a large tongue plate holding strength and hence extremely high engagement reliability. In this buckle apparatus, disengagement of the tongue plate 12 is effected by sliding the lock member 10 upwardly as viewed in FIG. 9.
In this type of buckle apparatus, the respective joint or slide surfaces of the lock member 10 and the buckle body members 14 may gradually become worn and roughened as a result of repetitive use of the seatbelt system, which leads to an increase in the force required for disengaging the tongue plate 12 and hence causes operability to be deteriorated.